The CDT 1.15 release note can be found here, http://docs.cray.com/books/S-9408-1404//S-9408-1404.pdf

Note:

The compiler wrappers from the current default craype/2.1.1 module no longer generate serial binaries that run on login nodes. You will see the following message if attempting to run serial codes on login nodes:

Please verify that both the operating system and the processor support Intel(R) F16C instructions

You configure script may fail as a result. We are working with Cray to resolve this issue. The workarounds are avaible here.